ackerman



P. ACKERMAN.

PARALLEL FEEDER PROTECTION.

' APPLICATION FLLED DEC. 24. I917. 1,333,892. Patented Mar. 16,1920.

3 SHEETS'SHEET I.

five-21702",-

P. ACKERMAN;

PARALLEL FEEDER PROTECTLON.- APPLICATION FILED DEC. 24, 1,91}.

Patented Mar. 16, 1920.

3 SHEETS-SHEET 2.

five/971702",

P. ACKERMAN.

PARALLEL FEEDER PROTECTION.

APPLICATION FILED DEC. 24, I917. 1,333,892. Patented Mar. 16, 1920.

3 SHEETS-SHEET 3- UNITED STATES PATENT OFFICE.

PAUL ACKERMAN, OF TORONTO, ONTARIO, CANADA, ASSIGNOR T0 SEARS B. CONDIT,JR.

PARALLEL-FEEDER PROTECTION.

Specification of Letters Patent. Patented )Iar. 16, 1920.

Application filed December 24, 1917. Serial No. 208,572.

To all whom it may concern:

Be it known that I, PAUL ACKERMAN, a citizen of Switzerland, and aresident of 'loronto, Province of Ontario, and Dominion of Canada, haveinvented an Improvement in Parallel-Feeder Protection, of which thefollowing is a specification.

My invention relates to electrical distribution systems, and hasparticular reference to the protectionof parallel feeders ass0- ciatedwith such systems.

It is common practice in distribution sys tems, where current is to betransmitted from a central power station to a distributing sub-station,to employ a number of parallel feeders extended between the power isation bus bars and the substation bus bars in order to providecontinuity of operation upon the possible failure of one or more of theparallel feeders.

Each of the parallel feeders is preferably normally arranged to haveapproximately the same operating characteristics; and all ofthe feedersare arranged to carry equal loads. It sometii'nes happens that a faultoccurs upon one of the parallel feeders of the system, and in such anevent it is therefore desirable that the faulty feeder be isolated fromthe system without interfering With the distribution of currentthroughout any of the other feeders of the system; and it is with meansto accomplish this result that my invention is concerned.

As previously stated, the feeders are normally adapted to carry equalcurrents. Upon the occurrence of a fault, such as a short, in any one ofthe feeders, the current flow in the faulty feeder is increased overthat of the remaining parallel feeders, and may become reversed indirection relative to the current flow in the remaining healthy feedersof the system.

Various protective systems have been conceived, i'naking use oftherelative increase and reversal of current flow. Such a sys I tern, forinstance, is disclosed in my Patent- 1,192,724, dated July 25th, 1916.

In the distribution system. illustrated in said patent, any particularparallel feeder controlling circuit is governed by the conditionexisting in the parallel feeder to be governed, and by the condition ofany two other parallel feeders of the system. This system has thedisadvantage that if the two parallel feeders associated with theparallel feeder to be protected are removed from the system, theparallel feeder will be protected only against straight overloads, andnot against relative reversal of current flow therein. I

It is highly desirable that the removal of one or more parallel feedersfrom the distribution system should not affect th operation of theprotective devices guarding the remaining feeders from the effects offaults developing within the feeders.

An object of my invention is in the provision of protective means forthe parallel feeders of a distribution s stem associated with all of theparallel feeders of the system, whereby the relative change of condition of any parallel feeder with respect to all of the other parallelfeeders, serves to operate to remove the faulty feeder from the system.

By governing any particular feeder by all the other feeders of thesystem, it may be seen that the removal from the system of any one ormore feeders up to a predetermined niunber, does not affectthe completecontrol and protection of the particular feeder chosen.

The means whereby I accomplish the object of my invention is in theprovision of current transformers associated in the line of all theparallel feeders, and so connected with each other and with relays that,upon the normal condition of the system, in which each parallel feederhas the same value of current flowing through it, and the system isbalanced; the current transformers, or the effects of the current fromthe transformer upon the relays will be balanced, and the relays willthereby be unoperated; but upon the development of a fault in any onefeeder, resulting in an increased current flow in that feeder or arelative reversal of current flow in that feeder with respect to theremaining feeders; the increased or reversed current flow in the currenttransformer of the faulty feeder will serve to unbalance the normallybalanced protective system in which the relays are included. and serveto operate the relays to selectively cut out the faulty feeder.

There are a number of ways in which the current transformers and relaysmay be connected between the parallel feeders of F or instance, inasmuchas the object of this inventlon is to connect the controlling orprotective circuit of any particular feeder wlth all ofthe otherparallel feeders,

a possible scheme of connection is to cor.

nect a current transformer in the particular feeder with the currenttransformer of particular feeder with currenttransformers in theremaining parallel feeders, forming pairs of connected feeders betweenthe particular feeder and all of the remaining feeders. If there arethree parallel feeders in the system, numbered respectively 1, 2 and 8,and feeder 1' is the feeder to be protected then there will beaconnectlon between a transformer in line 1 and a transformer in line 2,and a separate connection between a second transformer in line land'atransformer in line 3. v

Relays are associated in the connection between the pairs oftransformers; and the connection between the transformers and the relaysis such that, in the norn'ially balanced condition of the. circuit, therelays are ineffectively energized; but upon an unbalancing of theparticular feeder, with respect to the other feeders with which it isconnected, the relayswillbe operated; but both relays are arranged to beso connected as to collectively control the particular parallelfeeds-i3. and therefore, both relays must be operated to cutout theparticular parallelfeeder from the system. 1 I

While the connection above described illustrates the principle of thesystem, in that pairs of connections are made between the feeders, andprotective relays arranged in said connections, yet itispossible tocombine the relays and the current transformers in the feeders to form acertain minimum number, w rich will completely fulfil the requirementsofthe obj ect of the inrention.

In practice, there are two general'schemes of connections between thecurrent transformers associated in the parallel feeder circuits and therelays. It is possible to connect the transformers in series with thecoils of the relays and employ differential relays, in which conditionthe magnetic-flu in the relays will normally be bucking each other,andthe relays are thereby normally. ineffectively energized rand itispossible to'cornect the currenttransformers of the parallel feedersysteni'inseries and connect the coils of the relays, employing thistime non-dif- I 'ferential relay 1n shunt across the trans f01;'mers,1in which connection the relays are normally inefi'ectively energized.Both schemes of COHHQCtIOH are old in the'prior art, and areinterchangeably employed where the type of transformer and otherassociated instruments seems to justify the use of one systemratlierthanthe other.

In the figures, Figure 1 illustrates dia grammatically a protectivesystem showing the general scheme of connection, embodying my invention,associated with three par allel feeders.

Fig. 2 illustrates a protective system for three parallel feeders inwhich a minimum number of relays and current transformers are used, therelays being connected in series with the transformers.

Fig. 3 illustrates diagrammatically the scheme of connection forjthreeparallel feed ers employing series connected current transformers andshunt connected relays. I

Fig. a system of Fig. 3 in which a minimum number of transformers andrelays are employed. l

,Fig. illustrates a protective system for four parallel feeders,employing the series scheme of relay connection'and a minimum number oftransformersand relays.

6 is a protective system for four parallel feeders, employing the shuntscheme of relay connection and a minimum number of transformers andrelays: I I

As shown in F 1, the parallel feeders 10, 11 and 1-2 are connected tothe bus bar 1%, which i in represent the sub-station end of thedistribution system. Each parallel feederhas a switcn 15, in its circuitwhich when operated serves to disconnect its particular parallelfeederfrom the bus bar ll;

and each'switch has associated with it the" tripping cell 16, which isarranged to be governed by the protective relays to be hereinafterdescribed. I

The control circuit for any parallel feeder is associated with all ofthe other parallel feeders, and therefore line 10 associated with line11 and line 12 the condition of said lines'll andl2 being a dition ofline 10. Also line 11 isv associated .with line 10 and line 12, in whichcase the 1 condit on of said lines 10 and 12 form'a pairs of connectionswhich can be made between the current transformers of the parallelfeeders.

I In lcurrent transformers '17 are arranged in lin s '10 and ill-{andthe current coils or secom; ries thereof are respectively connected toth coils 18 and19 of a diffen' second current trans-Q ential relay 29.A. former 17", in line 10, and current transmeasure of the con- 7 r Ition between the circuits including the switch tripping coils 16 is suchthat two relays must be simultaneously closed in order to energize thetripping coils of the switch of a particular feeder, in order that saidfeeder may be removed from the system.

In the normal operation of the system, the coils 18 and 19 0f thedifferential relays 20, 21 and '22, in the pairs of connections betweenthe feeders of the system, are equally and oppositely energized, andconsequently all of the relays are in a non-operative position.

Upon the occurrence of a fault in feeder 10, for instance, the resultingincrease or reversal of current flow in the transformers 17 and 17connected in said feeder, relatively 1 to the current flow in thetransformers in the remaining parallel feeders of the system,

them to actcumulatively to cause the simultaneous operation of saidrelays" to close the contacts 23, which completes the oper atin gcircuit for the tripping coil 16 and the switch of the feeder 10 therebyoperates to disconnect said feeder from the bus bar 14.

The closing of contacts 24 of the relays and 21,upon theoperation ofsaid relays to isolate the feeder 10 from the system does not operate tocomplete the circuit for the tripping coil for any other feeder switch,

inasmuch as both of the separate trip coil circuits, controlled by thecontacts 24; of the relays 20 and 21, are also governed by the relay 22connected between the two normal or healthy feeders 11 and 12, and whichis thereby unaffected by the faulty condition of the feeder 10.

If the fault occurs in feeder 11 instead of in feeder 10, then therelays 20 and 22,, connected in the connections between parallel feeders11 and 10, and 11 and 12 respectively, operate to close contacts 2& ofthe relay 20, and 23 of relay22, to coninnctively control the operationof the trip coil for tl e switch in feeder 11, to isolate said feederfrom the bus bar 14;.

The trip coil circuits for the switches in the remaining and healthyfeeders 10 and 12 will be maintained openat the contacts controlled byrelay .21 which is unaffected by the condi the fault in e or M.

The ion of he protective system to isolate the feeder 12 from thedistribution ce of a fault in of current flow caused by connecticn withfeeders 10 illustrates a simplified arrangein the protective circuits ofFig. 1, embodying the scheme of pairs of connections between the p .llelfeeders, in which the feeders 10, 11 12 have but the current tran(-1'111" z' associated therewith, which tram rs are independently connected with a three differential relays 20, and 22. In the connectionshown, cur rent transformer 17 in line 10 is connected to the coils 18of relays 20 and 21. Transformer 17 in ine 11 is connected to the coil18 of din erential relay and the coil 19 of relay 20. Transform 17 ofline 12 is connected to the coil '19 of relay 22 and the coil 19 ofrelay Considering feeder 10, the two relays 20 and 21 are adapted forits protcction, and are c orerned by t the feeder 11. the r'r-nsftu'n erof which is Connected to the coil 19 of relay and hy feeder 12 thetransformer of 1 ch is connected tothe coil 19 of relay :1. The otherpairs connections between the 1GJ"211111l feeders are v connected to thecoils of the dif 12- ea "*lijttl COllClltlUll l. p ticularl'v to feedercm the energization botl in both relays 20 and 21 will the relays willthere fore n r t to close the contacts 23 and I f acted as in Fig. 1, totie tripping circuits or the switches 15 in. the feeders Unon theoccurrence of a faultin feed r 10 which results in an overload or a 'entflow therein relative to the coils 18 of the rebecoine energized ingreater proportion than the coils 19 of said relays, ch are connectedrespectively to the trans in feeders 11 and 12 and which are normallyenergized or in which, t 1 s there is no relative reversal of cur e land thereby both relays will be i-nltaneously operated to complete theconnection, through con-c s of the relays, with the trippi coil 16 tocause the opening of the s\ -ch 15 in the feeder 10, to thereby isolatethe feeder from the circuit. Upon a fault occurring in any other feeder,the same condition of affairs will he set up, and the proper relays willbe effectively energized to remove the faulty feeder from the system.

formers of the pairs of parallel feeders are connected in series and therelays are con nected 1n shunt across the connections between the pairsof current transformers.

. that in Fig. 3 there is a series connection of current coils, andshunt connection of relays. As here shown in Fig. 3, the current transformer 17 in feeder 10 is connected in series 'with the transformer 17of feeder 11. A second transformer 17 in feeder 10 is connected inseries with-a transformer 17 in feeder 12, thereby connecting line 10with all of the other feeders of the system. -A transformer 17 in feeder11 is connected in series with a transformer 17 in feeder 12, and feeds11. is thereby connected witlrall of the other feeders in the system,and line 12 is also connected wit-hall the other feeders in the system.

Relays 25, 26 and 27 are connected respectiyely in shunt across theconnections between the. transformers connecting feeder 10 with 11, 10with 12 and 11 with 12. In

I the normal and balanced condition of the feeders there is novoltage'drop across the relay coils; and consequently, the relays arenot operated. .Howeyer, 7 upon .an occurrence of a fault 111'f6QCl6l.10,for instance, the current in transformers l4 and 17 in said feeder willbecome greater than the [current in transformer 17; of feeder 11 and inthe transformer 17. of line 12; andtherefore the relays and 26 willbecome effectively energized and operate to close the 7 contacts 23controlled by said relays to energize the tripping coil 16, and causethe isolation of the faultyfeeder 10 from the system. other feeder willcause pair of relays to be operated in a similarmanner to remove thefaulty feeder from the system.

- In Fig. 4: isshown a simplified scheme of connections of theprotective system of Fig. 3, the'operation of which is exactly similarto the operation of the system shown in Fig. As here shown, the currenttransformers 17 1n the parallel feeders 10, 11 and 1.2 are connected inseries with'each other.

The relays 25, 26 and-Q27 are connected in,

, shunt across, the three transformers 17 in the feedercircuits, and,here shown, re lays 25 and 26, in series, are connected acrosstransformer 17 in line 10; relays and 27, in series, are connectedacross the transformer 17 in line 11; and relays 26 and 27 are connectedinserie's across the current coil 17 'in'line 12. It is seen that withthis scheme of connection, any particular feeder is connected with allthe other feeders...

7 Two relays must be operated to control the controlling circuit for'anyparticular feeders to be Tie occurrence of a fault in any feeder systemIn the operation of the system shown in Fig. at, in the normal andbalanced condition of the feeders, there is an equal current flow ineach of the current transformers in the feeders; and, consequently, therelays 25, 26 and 27, connected across these transformers will not beoperated, due to the absenceof a differ ence of potential at the pointsto which the relaysare connected. If, however, a fault develops infeeder 10, for instance, the current in the transformer 17 in saidfeeder to operate said switch to isolate the feeder from the system;Upon the occurrence-of a fault 1n any other feeder of the system saidfeeder Wlll be cut out of the systen'l in a manner similar to thatdescribed in regard to feeder 10. v x V Fig. 5 shows a simplified schemeof-conuections for a protectiy'e' systemrinvolying' four parallelfeeders, in which the current transformers are connected in series withthe relays governing .the tripping circuits. The relays in this case are"differential relays. 7 f

Inasmuch as there are four parallel ployed V r relays, which representsthe number of pairs of connections which may be made,

protected, there must bejemand which is the n'iinimunr number of 're- 7lays that may be employed to completely protect a system comprising fourfeeders, and which is connected between the parallel feeders of thesystem in accordance with 7 he invention Considering the case of any onefeeder, there are three remaining feeders to the system, and there mustof necessity be'three relays, each of which respec-:

parallel feeders in which the series connection of current coils and-theshunt connectlon of relays is. employed. "Inasmuch as there are threecombinations of one line,

considering any particular parallel feeder against the remaining threefeeders, it follows that there must be provision for three taps of threerelays corresponding to one line. WVith one transformer per line, thereis available but two such taps, and it thereforenecessary to employ atleast two transforn'iers for each line in order to provide the requisitenumber of taps to properly connect the three relays required tocompletely protect the line in question.

As here shown, feeders 10, 11 and 12 have each a transformer 17, whichare connected in series. A second transformer 17 in feeder 10 isseparately connected in series with a second current transformer 17 infeeder 12, and with atransformer 17 in feeder 13. A second transformer17' in line 11 is connected in series with a transformer 17 in feeder13, which connection is independent from the two previous sets oftransformer connections. Relays 28, 29 and 31 are connected to pointsbetween the transformers 17 in feeders 10, 11 and 12.

Relays 30 and 33 are connected across the connections betweentransformers 17" and 17 in feeders 10, 12 and 13 respectively, and

relay 32 is connected across the connections between the current coils17 in feeders 11 and 13.

By the arrangement of transformers and relays shown, any particularfeeder is connected with all the remaining feeders, and the operation ofthree relays serves to control the controlling or tripping circuit forthe switch of the particular feeders chosen.

In the operation of the protective system illustrated, in the normalcondition of equal current flow in all of the current transformers inthe parallel feeders, there is no potential difference between thepoints between the transformers to which the relays are connected, andconsequently the relays are not operated. Upon the occurrence of afault, say in feeder 10, a potential difference is set up across thetransformer 17 in said feeder, and relays 28 and 29 are energized, andoperate to close the contacts :23 and 24 controlled thereby. Theoperation of said relays alone does not, however. suflice to causethe'energization of the tripping coil 16 of the switch 15 of. the feeder10.

Due to the fault, the potential across transformer 17 in feeder 1.0,which transformer is connected with transformers 17 and 17' respectivelyin feeders 12 and 1", serves to energize relay 30, and the operation ofsaid relay 30 serves to complete the tripping circuit and cause theisolation of the faulty feeder 10 from the system.

No other tripping circuits will be affected inasmuch as other relays,arranged to be nnoperated upon the occurrence of a fault in feeder 10,must also be operated to control the tripping circuits for the otherfeeders.

A similar operation of the proper relays occur upon the occurrence of afault in any other feeder of the system.

As a general proposition, it may b stat d that with n feeders, the totalnumber of relays to adequately protect all the feeders is and the numberof relays that must be simultaneously operated to selectively remove anyfaulty feeder from the system is o1/1. If there are six feeders to beprotected, for instance, then the total, number of relays to adequatelyprotect all of the feeders is relays, and the number of relays that mustbe simultaneously operated to remove a feeder from the system is oneless than the total number of feeders in the system; or five relays.

In the cases above cited, a single phase line is illustrated. If a threephase line, or any multi-phase line is employed, the number of relaysmust be duplicated for each phase. The diagrams represent one end of thefeeder system, which may be the end connected with the sub station busbars. The other end of the feeder may be provided with exactly the sameequipment of relays, to isolate the faulty feeder from the system atthat end. The total. number of relays in any system will alwayscorrespond to the total possible number of pairs of con nections betweenfeeders, and the total num ber of relays in series to trip one switch toisolate the corresponding feeder from the system will be equal to thetotal number of pairs of connections between one feeder and theremaining parallel feeders.

In the lines above described, it has been assumed that the feeders haveapproxi mately the same characteristics. If one or more of the feedersare of different characteristics, then the windings of the relays, orthe transformers, associated with such feeders is so arranged as tocompensate for such difference.

I claim:

1. In an electrical distribution system comprising a plurality ofparallel feeders connected through switches with buses, connectionsbetween any particular feeder and all other feeders in the system, arelay in each connection, a tripping circuit for each feeder, each relayarranged to govern a plurality of tripping circuits, and means to causethe relays in the connections between a particular feeder and all otherfeeders to operate to selectively and conjointly control the trippingcircuit for the particular feeder to isolate said feeder from the busupon the occurrence of an abnormal current condition in said feeder.

2. In an electrical distribution system comprising a plurality ofparallel feeders connected through switches with buses, in-

nected hrough switches with buses, connec tions between the'feeders toform a combinatlon of pans of connected feeders between any particularfeeder and all other feeders of the system, a relay in the connectionbetween each pair of connected feeders, a tripping circuit for eachfeeder,

means to cause each relayto control a plu V rality of tripping circuits,and means to cause the relays in a particular combination to operate toconjointly control a particular tripping circuit upon the occurrence'ofan abnormal current condition in the corre sponding feeder to therebyisolate said feeder from the bus. I i

4:. In an electrical distribution system comprising plurality ofparallel feeders connected through switches with buses, inductiveconnections between thefeeders to form a combination of pairs ofconnected feedersbetween any particular feeder and all other feeders ofthe system, a relay in the connection between each pair of con nectedfeeders, atripping' circuit for each feeder, means to cause each relayto control a plurality of tripping circuits, and means to cause therelays in a particular combination to operate to congointly control. aparticular tripping circuit upon the occurrence of an abnormal'currentcondition in the corresponding feeder to thereby isolate said feederfrom the bus. V

5. In an electr cal distribution system comprising a plurality ofparallel feeders connected through switches with buses, induct-ireconnections between the feeders to form a combination of pairs ofconnected feeders between any particular feeder and all other feeders ofthe system, a relay in the connection between each pair of connectedfeeders, tripping circuit for each feeder, means to cause each relay tocontrol two tripping circuits, and means to select for operation certainrelays to conjointly control the tripping circuit of particular feederto isolate said feeders from the bus upon the 00- I currencc of anabnormal current condition in said feeder.

6. In an electrical distribution system p Z a comprising a plurality ofparallel feeders connected through switches with buses, inductiveconnections between the feeders to form a combination of pairs ofconnected feeders between any particular feeder and all other feeders ofthe system, a relay in the connection between each pair of connectedfeeders, mon to a plurality of such combinations, a tripping circuit foreach feeder, the relays included in a particular combination operable toconjointly control the tripping cir- 'transformer-sin said feeders,connections between the secondaries of said transformers to form 'acombination of pairs of inductively connected feeders between aparticular feeder and all other feeders of the system a relay in theconnection between each pair of connected feeders, thenumber of relaysbeing one less than the number of possible combinations, certain of saidrelays forming a part of more than onecombinm tion, a tripping circuitfor each feeder, the relays of a particular combination arranged tocontrol the feeder circuit of the feeder forming the combination withall other feeders, and means to cause the relays of the particularcombination to operate to certain of said relays being com i conjointlycontrol the particular} feeder to disconnect it from the bus upon theoccurrence of'an abnormal current condition in said feeder. e

8. In an electrical distributionsystem comprising a plurality ofparallel feeders connected through switches with buses, transformers insaid feeders'tripping' circuits for said feeders, plurality of relayseach arranged to control two tripping circuits, two or more relaysarranged to coin trol each tripping circuit, and connections betweensaid transformers, and relays to select certain of said'relays foroperation to conjointly control the tripping circuit for a particularfeederto isolate said feeder from the bus upon the occurrence of anabnormal H. B. DAVIS,

Gannrrwccn.

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